Process and apparatus for densifying powder metal compact to form a gear having a hub portion,and preferred powder metal compact shape for use therewith

Claim 2

A process for densifying a powder metal compact so as to form a product having (a) a main body portion, (b) a hub portion formed integrally with the main body portion, and (c) a bore extending through the main body and hub portions, said process comprising the steps of: placing the compact in a die cavity so as to be supported by a core rod means carried in said die cavity, applying an axial force to a partially formed hub portion of said compact so as to press the compact against a closed end portion of the die cavity and to fully densify the hub portion of the compact prior to full densification of the main body portion of the compact, and applying a separate axial force to a partially formed main body portion of said compact after full densification of said hub portion is substantially completed so as to prevent significant material flow between the hub portion and the main body portion.

Claim 3

The process of claim 1 wherein said axial forces are sequentially applied to said compact in a single stroke of a forming punch.

Claim 4

The process of claim 1 wherein said step of placing includes a step of pressing said compact into supported engagement with said core rod means so as to radially densify an inner surface defining the bore of the compact.

Claim 5

The process of claim 3 wherein said step of pressing of the compact into engagement with the core rod means forms a spline in the bore surface of the compact.

Claim 6

Apparatus for densifying a powder metal compact having (a) a partially formed hub portion, (b) a partially formed main body portion, and (c) a bore extending through the main body and hub portions, said apparatus being of a type which includes a die having a cavity defined therein for imparting a final shape to the compact being densified, a core rod means contained within said die for being received in the bore of the compact and for supporting the compact, and a punch means for applying axial forces to the compact contained within said die, the improvement in said punch means comprising a first punch element for applying a first axial force to the partially formed hub portion of a compact after the compact is received on said core rod means, said first punch element being positioned to reciprocate in the direction of the central longitudinal axis of the compact so as to apply said first axial force in a direction which presses the compact against a closed end portion of said die cavity to thereby fully densify the hub portion of the compact prior to full densification of the main body portion of the compact, a second punch element for applying a second axial force to the partially formed main body portion of the compact after full densification of said hub portion is substantially completed so as to prevent significant material flow between the hub portion and the main body portion, said second punch element being positioned to reciprocate in the same direction as said first punch element so as to apply said second axial force in a direction which presses the compact into conforming contact with all parts of said die, driving means for advancing said first and second punch elements toward said die to apply said axial forces to a compact contained therein, and sequencing means for delaying the application of said second axial force by said second punch element until full densification of said hub portion is substantially completed.

Claim 7

Apparatus for densifying a powder metal compact having (a) a partially formed hub portion, (b) a partially formed main body portion, and (c) a bore extending through the main body and hub portions, said apparatus being of a type which includes a die having a cavity defined therein for imparting a final shape to the compact being densified, a core rod means contained within said die for being received in the bore of the compact and for supporting the compact, and a punch means for applying axial forces to the compact contained within said die, the improvement in said punch means comprising a first punch element for applying a first axial force to the partially formed hub portion of a compact after the compact is received on said core rod means, said first punch element being positioned to reciprocate in the direction of the central longitudinal axis of the compact so as to apply said first axial force in a direction which presses the compact against a closed end portion of said die cavity to thereby fully densify the hub portion of the compact prior to full densification of the main body portion of the compact, a second punch element for applying a second axial force to the partially formed main body portion of the compact after full densification of said hub portion is substantially completed so as to prevent significant material flow between the hub portion and the main body portion, said second punch element being positioned to reciprocate in the same direction as said first punch element so as to apply said second axial force in a direction which presses the compact into conforming contact with all parts of said die, driving means for advancing said first and second punch elements toward said die to apply said axial forces to a compact contained therein, and sequencing means for delaying the application of said second axial force by said second punch element until full densification of said hub portion is substantially completed.

Claim 8

The apparatus of claim 5 wherein said first punch element includes a tubular member having an end face which substantially matches a terminal end face of the hub portion of said powder metal compact.

Claim 9

The apparatus of claim 6 wherein said second punch element comprises a tubular element positioned concentrically around said first punch element and wherein said second punch element has an end face which defines a back face of the main body portion of the final product to be produced.

Claim 10

The apparatus of claim 5 wherein said core rod means is provided with a spline configuration on its outer surface so as to form a spline configuration along the bore of said compact as the compact is pressed into position of said core rod means.

Claim 11

The apparatus of claim 8 wherein said first punch element includes a spline configuration on a surface which mates with the outer surface of said core rod means.

Claim 12

The apparatus of claim 7 wherein said first and second punch elements are mounted in a common ram structure driven by said driving means so that both of said punch elements are moved together toward said die with each forming stroke of the ram structure, and wherein said second punch element is resiliently mounted relative to said first punch element so that said second punch element is delayed in its forward movement, upon engaging a portion of said compact, until said first punch element has advanced for a sufficient distance to substantially completely densify the hub portion of the compact.

Claim 13

The apparatus of claim 5 wherein said die cavity has a configuration which establishes gear tooth profiles on a compact densified therein.

Claim 14

The apparatus of claim 5 wherein said powder metal compact has a shape which allows full insertion of the compact into said die cavity by the action of said first punch element and without a bending moment being applied to the main portion of the compact relative to its hub portion.